Cambridge A Level Chemistry 9701 — 2010 Oct/Nov Paper 3 · Variant 5

This document consists of 13 printed pages and 3 blank pages. DC (NF) 28264/3 © UCLES 2010 [Turn over UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS General Certificate of Education Advanced Subsidiary Level and Advanced Level * 4 8 2 7 3 9 6 4 7 7 * CHEMISTRY 9701/35 Advanced Practical Skills October/November 2010 2 hours Candidates answer on the Question Paper. Additional Materials: As listed in the Instructions to Supervisors READ THESE INSTRUCTIONS FIRST Write your Centre number, candidate number and name on all the work you hand in. Give details of the practical session and laboratory where appropriate, in the boxes provided. Write in dark blue or black pen. You may use a soft pencil for any diagrams, graphs or rough working. Do not use staples, paper clips, highlighters, glue or correction fluid. DO NOT WRITE IN ANY BARCODES. Answer all questions. You may lose marks if you do not show your working or if you do not use appropriate units. Use of a Data Booklet is unnecessary. Qualitative Analysis Notes are printed on pages 13 and 14. At the end of the examination, fasten all your work securely together. The number of marks is given in brackets [ ] at the end of each question or part question. Session Laboratory For Examiner’s Use 1 2 3 Total

2 9701/35/O/N/10 © UCLES 2010 For Examiner’s Use 1 FA 1 is an aqueous solution of hydrochloric acid, HCl. FA 2 is aqueous sodium hydroxide containing 10.00 g dm–3 NaOH. You are to determine the concentration, in mol dm–3, of the hydrochloric acid in FA 1. (a) Method Fill a burette with • FA 2. Pipette 10.0 cm • 3 of FA 1 into a conical flask. Add to the flask a few drops of the acid-base indicator provided. • Place the flask on a white tile. • Titrate the acid in the flask with • FA 2. You should perform a rough titration. In the space below record your burette readings for this rough titration. The rough titre is … cm3. Carry out as many accurate titrations as you think necessary to obtain consistent • results. Record in a suitable form below all of your burette readings and the volume of • FA 2 added in each accurate titration. Make certain any recorded results show the precision of your practical work. • [7] (b) From your titration results obtain a suitable value to be used in your calculation. Show clearly how you have obtained this value. 10.0 cm3 of FA 1 required … cm3 of FA 2. [1] I II III IV V VI VII

3 9701/35/O/N/10 © UCLES 2010 [Turn over For Examiner’s Use Calculations Show your working and appropriate significant figures in the final answer to each step of your calculations. (c) (i) Calculate the concentration, in mol dm–3, of the sodium hydroxide in FA 2. FA 2 contains 10.00 g dm–3 NaOH. [Ar: H, 1.0; O, 16.0; Na, 23.0] The concentration of sodium hydroxide in FA 2 is … mol dm–3. (ii) Calculate how many moles of sodium hydroxide are contained in the volume recorded in (b). … mol of NaOH. (iii) Deduce how many moles of hydrochloric acid were pipetted into the conical flask and calculate the concentration, in mol dm–3, of the hydrochloric acid in FA 1. NaOH(aq) + HCl(aq) NaCl(aq) + H2O(l) The concentration of the hydrochloric acid in FA 1 is … mol dm–3. [2] [Total: 10] I II

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5 9701/35/O/N/10 © UCLES 2010 [Turn over For Examiner’s Use 2 FA 3 is crushed impure calcium carbonate, CaCO3. FA 4 is 0.500 mol dm–3 hydrochloric acid FA 5 is 0.280 mol dm–3 sodium hydroxide. You are to determine the percentage purity of calcium carbonate by dissolving a measured mass of FA 3 in a known volume of hydrochloric acid, which is in excess. The hydrochloric acid remaining after all the calcium carbonate has dissolved can be determined by titration with aqueous sodium hydroxide, FA 4. You may assume that any impurity present in the calcium carbonate does not react with hydrochloric acid. (a) Method – Read through the instructions before starting any practical work. Weigh and record the mass of an empty boiling-tube. • Add to the boiling-tube between 2.60 g and 2.80 g of • FA 3. Reweigh the tube and its contents. • In part • (b) of the method you will tip the FA 3 into hydrochloric acid, then re-weigh the tube and any residual FA 3. In the space below record, in an appropriate form, all of the balance readings and the mass of FA 3 used in the experiment. [2] (b) Method – Read through the instructions before starting any practical work. Pour approximately 150 cm • 3 of FA 4 into a 250 cm3 beaker. Add, a little at a time with constant stirring, the weighed • FA 3 to the acid in the beaker. After each small addition stir until the effervescence has ceased and all the solid • has dissolved. Reweigh the tube and any residual • FA 3. Record the mass in (a). Transfer the solution in the beaker to the 250 cm • 3 graduated (volumetric) flask labelled FA 6. Rinse the beaker several times with • a small amount of FA 4 and add the rinsings to the graduated flask. Make up the solution to the 250 cm • 3 mark by adding FA 4, not water. Shake the flask to obtain a uniform solution. • I II

6 9701/35/O/N/10 © UCLES 2010 For Examiner’s Use Titration Fill a burette with • FA 5. Pipette 25.0 cm • 3 of FA 6 from the graduated flask into a conical flask. Add to the flask a few drops of the acid-base indicator provided. • Place the flask on a white tile. • Titrate the acid in the flask with • FA 5. You should perform a rough titration. In the space below record your burette readings for this rough titration. The rough titre is … cm3. Carry out as many accurate titrations as you think necessary to obtain consistent • results. Record in a suitable form below all of your burette readings and the volume of • FA 5 added in each titration. Make certain any recorded results show the precision of your practical work. • [2] (c) From your titration results obtain a suitable value to be used in your calculation. Show clearly how you have obtained this value. 25.0 cm3 of FA 6 required … cm3 of FA 5. I II

7 9701/35/O/N/10 © UCLES 2010 [Turn over For Examiner’s Use (d) Calculations Show your working and appropriate significant figures in the final answer to each step of your calculations. Remember – FA 4 is 0.500 mol dm–3 hydrochloric acid FA 5 is 0.280 mol dm–3 sodium hydroxide. (i) Calculate how many moles of sodium hydroxide are contained in the volume recorded in (c). … mol of NaOH (ii) Deduce how many moles of hydrochloric acid reacted with the sodium hydroxide in (i) and calculate how many moles of hydrochloric acid were present in the 250 cm3 graduated flask labelled FA 6. NaOH(aq) + HCl(aq) NaCl(aq) + H2O(l) … mol of HCl were present in the graduated flask. (iii) Calculate how many moles of hydrochloric acid were present in 250 cm3 of FA 4. 250 cm3 of FA 4 contained … mol HCl. (iv) Calculate the following. (answer to (d)(iii) – answer to (d)(ii)) This is the amount of hydrochloric acid that reacted with the calcium carbonate in the weighed sample of FA 3. … mol of HCl reacted with the calcium carbonate in … g FA 3. I II

8 9701/35/O/N/10 © UCLES 2010 For Examiner’s Use (v) Use your answer to (iv) to calculate the mass of calcium carbonate that reacted with hydrochloric acid. This is the mass of pure CaCO3 in the weighed sample of FA 3. CaCO3(s) + 2HCl(aq) CaCl2(aq) + CO2(g) + H2O(l) [Ar: Ca, 40.0; C, 12.0; O, 16.0] The weighed sample of FA 3 contains … g of CaCO3. (vi) Calculate the percentage of calcium carbonate, CaCO3, in FA 3 by evaluating the following expression. mass of CaCO3 from (d)(v) mass of FA 3 used, from (a) × 100 Complete your evaluation even if your answer is greater than 100% FA 3 contains … % calcium carbonate. [5] (e) 6.25 g of pure calcium carbonate are required to neutralise all the hydrochloric acid in 250 cm3 of FA 4. You were instructed to measure a mass between 2.60 g and 2.80 g of FA 3 in this experiment. What difficulties might you encounter if you used a mass of about 5.50 g of FA 3 in this experiment? … … … [1] III IV V

9 9701/35/O/N/10 © UCLES 2010 [Turn over For Examiner’s Use (f) (i) Complete the following table. The balance used in the experiment displays the mass to … decimal places. The maximum error in a single balance reading is ± … g. The maximum error in measuring the mass of FA 3 is ± … g. (ii) Calculate the maximum percentage error in the mass of FA 3 measured in (a). The maximum error in the mass of FA 3 is … %. [2] (g) (i) The percentage of calcium carbonate in the weighed sample of FA 3 can also be found by investigating the thermal decomposition of the compound into calcium oxide and carbon dioxide. Write a balanced equation, including state symbols, for this thermal decomposition. (ii) Briefly outline the key measurements to be made in order to find the percentage of calcium carbonate in FA 3 by this method. 1. … 2. … 3. … 4. … 5. … 6. … (You do not have to use all of the numbered steps in your answer) [2] [Total: 14]

10 9701/35/O/N/10 © UCLES 2010 For Examiner’s Use 3 FA 7, FA 8 and FA 9 are aqueous solutions, each containing one cation and one anion from those listed on pages 13 and 14 in the Qualitative Analysis Notes. At each stage of any test you are to record details of the following. colour changes seen • the formation of any precipitate • the solubility of such precipitates in an excess of the reagent added • Where gases are released they should be identified by a test, described in the appropriate place in your observations. You should indicate clearly at what stage in a test a change occurs. Marks are not given for chemical equations. No additional tests for ions present should be attempted. If any solution is warmed, a boiling-tube MUST be used. Rinse and reuse test-tubes wherever possible. (a) Use aqueous sodium hydroxide and aqueous ammonia, in separate tests, to identify the cation present in FA 7, FA 8 and FA 9. Present your results for each of the solutions in a suitable form below. Conclusion Complete the following table. solution cation supporting evidence FA 7 FA 8 FA 9 [6] I II III IV V VI

11 9701/35/O/N/10 © UCLES 2010 [Turn over For Examiner’s Use (b) (i) FA 7, FA 8 and FA 9 each contain a single anion which may be Cl –, I– or SO4 2–. Suggest a reagent that would enable you to identify any solutions containing SO4 2–. Reagent … Use this reagent to test each of the solutions. Record your observations in the table below. Indicate, with a tick in the final column, any solution containing SO4 2–. solution observation SO4 2– present FA 7 FA 8 FA 9 (ii) Select a further reagent that will enable you to identify the halide ion present in any remaining solution(s). Reagent ……………………………………………………….……………………….. Use this reagent to test the remaining solution(s). Record your observations and the identity of the halide in a suitable form in the space below. [5] I II III IV V

12 9701/35/O/N/10 © UCLES 2010 For Examiner’s Use (c) FA 10 is a white crystalline solid which turns into another white solid, FA 11, when heated strongly. Carry out the tests on FA 10 and FA 11 in the table below. Observe carefully at each stage and record all of your observations in the table. test observations (i) Place 1 spatula measure of FA 10 in a hard glass test-tube. Heat the solid very strongly until no further change is seen. (ii) Place 1 small spatula measure of FA 11 in a test-tube and add 1 cm depth of dilute hydrochloric acid. As soon as you have completed your observation in (ii), fill the test-tube with water. [5] [Total: 16] I II III IV V

13 9701/35/O/N/10 © UCLES 2010 [Turn over Qualitative Analysis Notes Key: [ppt. = precipitate] 1 Reactions of aqueous cations ion reaction with NaOH(aq) NH3(aq) aluminium, Al 3+(aq) white ppt. soluble in excess white ppt. insoluble in excess ammonium, NH4 +(aq) no ppt. ammonia produced on heating – barium, Ba2+(aq) no ppt. (if reagents are pure) no ppt. calcium, Ca2+(aq) white ppt. with high [Ca2+(aq)] no ppt. chromium(III), Cr3+(aq) grey-green ppt. soluble in excess giving dark green solution grey-green ppt. insoluble in excess copper(II), Cu2+(aq) pale blue ppt. insoluble in excess blue ppt. soluble in excess giving dark blue solution iron(II), Fe2+(aq) green ppt. turning brown on contact with air insoluble in excess green ppt. turning brown on contact with air insoluble in excess iron(III), Fe3+(aq) red-brown ppt. insoluble in excess red-brown ppt. insoluble in excess lead(II), Pb2+(aq) white ppt. soluble in excess white ppt. insoluble in excess magnesium, Mg2+(aq) white ppt. insoluble in excess white ppt. insoluble in excess manganese(II), Mn2+(aq) off-white ppt. rapidly turning brown on contact with air insoluble in excess off-white ppt. rapidly turning brown on contact with air insoluble in excess zinc, Zn2+(aq) white ppt. soluble in excess white ppt. soluble in excess [Lead(II) ions can be distinguished from aluminium ions by the insolubility of lead(II) chloride.]

14 9701/35/O/N/10 © UCLES 2010 2 Reactions of anions ion reaction carbonate, CO3 2– CO2 liberated by dilute acids chromate(VI), CrO4 2–(aq) yellow solution turns orange with H+(aq); gives yellow ppt. with Ba2+(aq); gives bright yellow ppt. with Pb2+(aq) chloride, Cl –(aq) gives white ppt. with Ag+(aq) (soluble in NH3(aq)); gives white ppt. with Pb2+(aq) bromide, Br–(aq) gives cream ppt. with Ag+(aq) (partially soluble in NH3(aq)); gives white ppt. with Pb2+(aq) iodide, I–(aq) gives yellow ppt. with Ag+(aq) (insoluble in NH3(aq)); gives yellow ppt. with Pb2+(aq) nitrate, NO3 –(aq) NH3 liberated on heating with OH–(aq) and Al foil nitrite, NO2 –(aq) NH3 liberated on heating with OH–(aq) and Al foil, NO liberated by dilute acids (colourless NO → (pale) brown NO2 in air) sulfate, SO4 2–(aq) gives white ppt. with Ba2+(aq) or with Pb2+(aq) (insoluble in excess dilute strong acid) sulfite, SO3 2–(aq) SO2 liberated with dilute acids; gives white ppt. with Ba2+(aq) (soluble in excess dilute strong acid) 3 Tests for gases gas test and test result ammonia, NH3 turns damp red litmus paper blue carbon dioxide, CO2 gives a white ppt. with limewater (ppt. dissolves with excess CO2) chlorine, Cl2 bleaches damp litmus paper hydrogen, H2 “pops” with a lighted splint oxygen, O2 relights a glowing splint sulfur dioxide, SO2 turns acidified aqueous potassium dichromate(VI) from orange to green

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16 9701/35/O/N/10 © UCLES 2010 Permission to reproduce items where third-party owned material protected by copyright is included has been sought and cleared where possible. Every reasonable effort has been made by the publisher (UCLES) to trace copyright holders, but if any items requiring clearance have unwittingly been included, the publisher will be pleased to make amends at the earliest possible opportunity. University of Cambridge International Examinations is part of the Cambridge Assessment Group. Cambridge Assessment is the brand name of University of Cambridge Local Examinations Syndicate (UCLES), which is itself a department of the University of Cambridge. BLANK PAGE

UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS GCE Advanced Subsidiary Level and GCE Advanced Level MARK SCHEME for the October/November 2010 question paper for the guidance of teachers 9701 CHEMISTRY 9701/35 Paper 3 (Advanced Practical Skills), maximum raw mark 40 This mark scheme is published as an aid to teachers and candidates, to indicate the requirements of the examination. It shows the basis on which Examiners were instructed to award marks. It does not indicate the details of the discussions that took place at an Examiners’ meeting before marking began, which would have considered the acceptability of alternative answers. Mark schemes must be read in conjunction with the question papers and the report on the examination. • CIE will not enter into discussions or correspondence in connection with these mark schemes. CIE is publishing the mark schemes for the October/November 2010 question papers for most IGCSE, GCE Advanced Level and Advanced Subsidiary Level syllabuses and some Ordinary Level syllabuses.

Page 2 Mark Scheme: Teachers’ version Syllabus Paper GCE A / AS LEVEL – October/November 2010 9701 35 © UCLES 2010 Question Sections Indicative material Mark PDO Layout I Volume given for Rough titre. and accurate titre details tabulated. 1 MMO Collection II Follows instructions – initial and final burette readings recorded for Rough titre and initial and final burette readings and volume of FA 2 added recorded for each accurate titre and headings should match readings. Do not award this mark if: 50(.00) is used as an initial burette reading; more than one final burette reading is 50.(00); any burette reading is greater than 50.(00) 1 MMO Decisions III Has two uncorrected, accurate titres within 0.1 cm3 Do not consider the Rough even if ticked. Do not award this mark if having performed two titres within 0.1 cm3 a further titration is performed which is more than 0.10 cm3 from the closer of the initial two titres, unless a fourth titration, within 0.1 cm3 of the third titration has also been carried out. 1 1 (a) PDO Recording IV All accurate burette readings (initial and final) recorded to nearest 0.05 cm3 Assess this mark on burette readings only 1 MMO Quality V, VI and VII Round any burette readings to the nearest 0.05 cm3. Check and correct subtractions in the titre table. Select the “best” titre using the hierarchy: two identical; titres within 0.05 cm3; titres within 0.1 cm3; etc. Award V, VI and VII for a difference from Supervisor within 0.20 cm3 Award V and VI only for a difference of 0.20+ cm3 – 0.30 cm3 Award V only for a difference of 0.30+ - 0.50 cm3 If the “best” titres are ≥ 0.50 cm3 apart cancel one of the Q marks. 3 [7]

Page 3 Mark Scheme: Teachers’ version Syllabus Paper GCE A / AS LEVEL – October/November 2010 9701 35 © UCLES 2010 (b) ACE Interpretation Calculates the mean, correct to 2 decimal places from any accurate titres within 0.20 cm3. The third decimal place may be rounded to the nearest 0.05 cm3. A mean of exactly .x25 or .x75 is allowed but the candidate may round up or down to the nearest 0.05 cm3. If ALL burette readings are given to 1 decimal place then the mean can be given to 1 decimal place if numerically correct without rounding. Mean of 24.3 and 24.4 = 24.35 (✓) Mean of 24.3 and 24.4 = 24.4 () Titres to be used in calculating the mean must be clearly shown – in an expression or ticked in the titration table. 1 [1] I Correctly evaluates 40 00 . 10 = 0.25(0) 1 1 (c) ACE Interpretation II Uses answer (i) × 1000 titre mean in step (ii) and answer (ii) x 10 1000 in step (iii) If an answer, with no working, is given in any section allow if correct. [2] Total [Total: 10]

Page 4 Mark Scheme: Teachers’ version Syllabus Paper GCE A / AS LEVEL – October/November 2010 9701 35 © UCLES 2010 2 (a) PDO Recording I Has correct headings (minimum three) and units in the weighing table in (2)(a) and correct units in the titration table in (2)(b) Acceptable units are /g, (g), mass in grams, mass in g; similarly /cm3, II All three balance reading are read with constant precision (same no of decimal places) and to at least 1 decimal place 1 1 [2] On Supervisor script scale the titre for 3.00 g of FA 3 added to the acid. Calculate 8 × (3.00 – mass of FA 3 used) and subtract from the titre obtained. Mass of FA 3 used = (mass tube + FA 3) – (mass tube + residue) If (mass tube + residue) < mass of empty tube then use (mass tube + FA 3) – (mass tube). (b) MMO Quality Award I and II if the difference between candidate and Supervisor scaled titres is within 0.40 cm3 Award I only if the difference is between 0.50+ cm3 and 0.80 cm3 1 1 [2] (c) There is no mark available for this section. (d) ACE Interpretation PDO Display I Uses 1000 titre mean × 0.280 in step (i) and uses answer (i) × 25 250 in step (ii) II Correctly evaluates 1000 250 5 . 0 × = 0.125 in step III Uses answer (iv) × 0.5 × 100 in step (v) IV Working shown in a minimum of three sections Working should be a step in the right direction: step (i) 0.28 × titre volume (in cm3/dm3) step (ii) Use of 25 & 250 or 10 step (iii) 0.5 and 250 step (iv) the correct two numbers step (v) would need to include 2 (0.5) and 100 step (vi) must be correct V 3 to 5 significant figures in final answers to all sections attempted – minimum of three final answers required 1 1 1 1 1 [5]

Page 5 Mark Scheme: Teachers’ version Syllabus Paper GCE A / AS LEVEL – October/November 2010 9701 35 © UCLES 2010 (e) ACE Conclusions Explains one of the following: If 5.5 g of CaCO3 had been used the titre would be too small/not enough HCl remains for the titration (not ‘all the acid has reacted’) or Difficult/takes too long to dissolve 5.5 g of solid/it will not all dissolve in 150 cm3 (of acid) or Excessive/too fast effervescence/fizzing/rate of gas evolved or Acid spray 1 [1] (f) ACE Interpretation (i) If balance displays to 1 decimal place: error in balance reading is ±0.05 g or ±0.1(0) g error in mass of FA 3 is ±0.1 g or ±0.2 g If balance displays to 2 decimal places: error in balance reading is ±0.005 g or ±0.01 g error in mass of FA 3 is ±0.01 g or ±0.02 g If balance displays to 3 decimal places: error in balance reading is ±0.0005 g or 0.001g error in mass of FA 3 is ±0.001 g or ±0.002 g (ii) Correctly evaluates to at least 2 significant figures: 100 used 3 FA of mass 3 FA of mass in error s candidate' × 1 1 [2] (g) ACE Conclusions ACE Improvements (i) Gives correct equation for the thermal decomposition of calcium carbonate including state symbols (ii) Outlines: weigh container weigh container + solid (heating and) weighing again repeated (heating and) weighing to constant mass or weigh container weighing container + solid (heating and) measuring gas volume when no further increase and cooled to room temperature / use of pV = nRT / T V P = constant 1 1 [2] Total [14]

Page 6 Mark Scheme: Teachers’ version Syllabus Paper GCE A / AS LEVEL – October/November 2010 9701 35 © UCLES 2010 FA 7 is Fe2(SO4)3(aq); FA 8 is CrCl3(aq); FA 9 is ZnI2(aq) [ZnCl2 + KI] 3 (a) PDO Layout MMO Collection ACE Conclusions I (Tabulates) observations clearly, showing: observation when each reagent is first added and observation when reagent added to excess (if there is a ppt) II, III and IV 1 mark for correct observations in each of the columns or rows representing FA 7, FA 8 and FA 9 or 1 mark for correct observations in the row or column representing a reagent added (initial and excess count as one row/column) Award V only if one ion only is correctly identified Award V and VI if all three ions are correctly identified from candidate’s observations. Allow ecf* 1 3 1 1 [6] Minimum for observations marks: Solution FA 7 FA 8 FA 9 NaOH red-brown/brown/rust ppt insoluble (in excess) grey-green ppt soluble/dissolves (in excess) giving a dark green solution White/milky white ppt soluble/dissolves (in excess) NH3 red-brown ppt insoluble (in excess) (suitable qualified brown) grey-green ppt insoluble (in excess) White/milky white ppt soluble/dissolves (in excess) Minimum for conclusions marks: (with incomplete but not CON observations) FA 7 red-brown ppt with either; FA 8 grey-green ppt with either/(dark) green solution with excess NaOH; FA 9 white ppt soluble in excess NH3. * ecfs allowed FA 8 allow Fe2+ if green ppt insoluble in excess NaOH (no grey-green ppts) FA 9 allow Al3+ and Pb2+ if white ppt insoluble in excess NH3 FA 9 allow Ba2+ and NH4 + if no ppt with either FA 9 allow Mg2+ if white ppt insoluble in excess of both

Page 7 Mark Scheme: Teachers’ version Syllabus Paper GCE A / AS LEVEL – October/November 2010 9701 35 © UCLES 2010 (b) MMO Decisions MMO Collection MMO Decisions MMO Collection ACE Conclusions I Selects barium chloride or barium nitrate for the test in step (i) Do not allow Ba2+ alone Ba2+(aq) or soln containing Ba2+ (ions) is acceptable II Records white/off-white precipitate with only FA 7 III Selects silver nitrate or lead nitrate in (ii) to add to the solutions (that do not contain sulfate) Do not allow Ag+ or Pb2+ alone Aqueous ions or solutions containing the ion are acceptable as above IV Appropriate observations FA 8 white ppt with Ag+/white ppt or no ppt with Pb2+ FA 9 yellow ppt with either Ignore observations with any solution candidate has identified as sulfate V FA 8 is chloride, FA 9 is iodide Credit if the supporting evidence fits the ion identified and the practical performed for FA 8 and FA 9 provided there is no CON observation in (i) Do not credit if Ag+ gives a ppt with FA 7 Marks IV and V may be awarded from FA 8 white ppt chloride (IV) FA 9 yellow ppt iodide (V) 1 1 1 1 1 [5] Other possibilities: Two white ppts with aqueous Ba2+ then remaining solution tested with aqueous Ag+/Pb2+ This would score marks I, III and may score one of IV or V Aqueous Ba2+ gives positive result with solution other than FA 7 and tests with aqueous Ag+/Pb2+ performed (This would score marks I and III) Ignore observation and conclusion with FA 7 Award correct observation and valid conclusion for third ion thus scoring one of IV or V Aqueous Ba2+ gives positive result with all three solutions Award mark I, and mark III may be awarded for selection of aqueous Ag+/Pb2+ or statement that no further testing is required but no other marks can be awarded in this section.

Page 8 Mark Scheme: Teachers’ version Syllabus Paper GCE A / AS LEVEL – October/November 2010 9701 35 © UCLES 2010 FA 10 is NaNO3(s); FA 11 is NaNO2(s) (c) (i) (ii) MMO Collection MMO Decisions MMO Collection I Solid/FA 10 melts/to a liquid/solution (on heating) II Observes bubbles of gas in liquid/solution or Liquid/solution turns yellow/pale yellow III Describes an appropriate test in either (i) or (ii) for any of the following gases: O2, CO2, NH3 or SO2 There must be a reference to gas being evolved before this mark can be awarded. IV Positive identification of oxygen gas in (i): glowing splint rekindles/relights/glows brighter (gas evolved rekindles a glowing splint would gain marks III and IV) (‘glowing splint rekindles’ would gain mark III not IV) V On adding acid to residue to FA 11, observes brown/yellow-brown gas (not yellow, orange or red-brown) or blue solution (allow greenish blue) 1 1 1 1 1 [5] Total [16]